Presently, measuring devices in the form of densitometers or colorimetric measuring devices are used on printing machines in order to determine parameters relevant to the print quality. These measuring devices are used, in particular, for inspecting the measuring fields of a print control strip of a printed product. Actual values of parameters relevant to the printing process can be determined from the measured values from the densitometer and/or the colorimetric measuring device and compared with predetermined nominal values for quality control purposes. Based on this comparison, the printing machine can be adjusted accordingly, e.g., the ink can be adjusted.
Densitometers as well as colorimetric measuring devices utilize an integral functional image of a measuring field to be inspected in order to determine an actual value of a parameter relevant to the print quality of this measuring field. However, this does not take into account whether the measuring field as such is neatly printed. If the measuring field is not neatly or homogenously printed due to insufficient contact pressure between the plate cylinder and the blanket cylinder or due to a defective or soiled rubber blanket, the densitometer or the colorimetric measuring device does not deliver an exact actual value such that, for example, an ink control system based on such an actual value can lead to inferior printing results.